Closed Captions

ATSC 3.0 Forum
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Matt832
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Joined: Thu Jul 19, 2018 3:22 pm

Closed Captions

Post by Matt832 »

I'm receiving ATSC 3.0 from the Detroit tower. The quality is great but I have yet to get any closed captions. Am I doing something wrong? I find it frustrating since I use them all the time. I use ChannelsDVR 98% of the time, other than that I use the tuner with my LG CX OLED. Wondering how to implement them in my setup.

nickk
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Re: Closed Captions

Post by nickk »

Hi,

Closed Captioning is a feature of the player/client device. If you are using Channels DVR you will need to ask them to support ATSC 3.0 closed captioning.

Nick

signcarver
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Re: Closed Captions

Post by signcarver »

To make it more relevant to what nickk mentioned (and to put it back in his court), with the HDHomeRun app I will not get any captions with ATSC 3.0 stations on any platform I have tried.

With "channels", I can get captions off of physical channel 35 (each virtual channel off of 35) here in phoenix as VLC will report 4 "streams" of EIA-608 subtitles (also known as line 21 captions). On physical channel 27 each virtual channel has no EIA-608 subtitles reported. However a regular ATSC 3.0 TV can usually pick up captions on those streams. My understanding is that it is expected that ATSC 3.0 streams will put captions as separate subtitle streams in the manifest and I am not sure if those are available to the TS the HDHomeRun puts out (haven't gone looking at the recordings since ATSC3 rarely is the choice recording for me) but they may be there but may just need to be implemented which I believe would be more like DVB subtitles.

It is also my understanding that such is kind of a moving target that everything isn't completely standardized on (i.e. even some NextGen TV's may also need updates as they might handle only "9 out of 10 ways" to put captions on the stream --making up those numbers, I do not know how many ways there are (I suspect the number is closer to 3-5 ways) but know some TV's don't support all or should I say some TV's support some more better than others). As a result a few have mentioned it might be better for SD to wait a bit before introducing ATSC 3.0 captions. As a result I don't expect anything soon but thought they had DVB subtitles working now (I know for a long time they didn't) so it may not be a lot of work to offer some captions. It may also require firmware updates to encode specific tracks in a more friendly way.

nickk
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Re: Closed Captions

Post by nickk »

With ATSC 3.0 subtitles are delivered in XML files along with the audio and video segments. When the HDHomeRun converts to TS format the audio, video, and subtitles are delivered as elementary streams.

Nick

Matt832
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Joined: Thu Jul 19, 2018 3:22 pm

Re: Closed Captions

Post by Matt832 »

i flipped over to the LG CX and using the HomeRun app did not get any CC on the ATSC 3.0 feeds. So I do not believe it's a "Channels" thing. Is it conceivable that none of the 5 streams of network shows support CC?

nickk
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Re: Closed Captions

Post by nickk »

Matt832 wrote: Mon Oct 04, 2021 10:00 pm i flipped over to the LG CX and using the HomeRun app did not get any CC on the ATSC 3.0 feeds. So I do not believe it's a "Channels" thing. Is it conceivable that none of the 5 streams of network shows support CC?
The currently released HDHomeRun firmware delivers ATSC 3.0 closed captions to the client app.
The currently released HDHomeRun app does not include support for ATSC 3.0 closed captions.

As to if captions are in the broadcast, your ATSC 3.0 capable TV would be the test.

Nick

w4cl
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Re: Closed Captions

Post by w4cl »

Matt832 wrote: Mon Oct 04, 2021 10:00 pm
As to if captions are in the broadcast, your ATSC 3.0 capable TV would be the test.
The FCC requires stations to maintain closed captions in ATSC 3.0 as they do in ATSC 1.0. There is no exemption. I know there is a release for Sony ATSC 3.0 compatible TV's where the captions are not working correctly, but the next revision of that software will have that bug corrected according to Sony.

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